The present invention relates to controlling an implantable device, e.g., an implantable medical device, and more particularly to using an RF telemetry link to establish and maintain communications with the implantable device.
Due to a multitude of advances in electronics, packaging, sensors, pumps, and pharmacology, implantable devices such as stimulators, pumps, and sensors are becoming increasingly more complex. However, communication with implants has not advanced significantly over the past decade.
Conventional implantable devices (e.g., pacemakers) implement a relatively simple form of establishment and maintenance of communication with external devices. Some devices contain a magnetic sensor, and a communication session is established when an external permanent magnet is brought into close proximity (e.g., within a few centimeters), triggering the magnetic sensor. The magnetic sensor may also be used for communication, e.g., the presence of a permanent magnet for a certain period of time may adjust a parameter or toggle the state of activation of the implantable device. Such a system of establishing and maintaining communication may be triggered erroneously by a strong magnetic field in the environment. Also, the complexity and speed of communication is inherently limited.
Other devices communicate via an inductive link. In these systems, a communication session may be established when an external coil is energized, producing a strong magnetic field, and is then brought into close proximity with an implanted coil contained within or next to the implant. This system has the advantage that the implantable device may be a passive receiver, i.e., the energy received in its coil may provide all of the energy required for causing activation of the implant and initiating a communication session. This allows the implant to expend virtually no energy in its receiver outside of communication sessions. However, such a system also has disadvantages. The inductive magnetic fields decrease rapidly with distance, and thus the external device must be in close proximity to the implant (e.g., within a few centimeters). Also, since the energy to activate the implant may be provided by the external device, the external device requires a relatively sizeable source of power. Such a strong magnetic field may also be difficult to modulate efficiently, and this may lead to either an increased power expenditure or a relatively low limit on communication bandwidth.
Conventional implant systems generally operate in a relatively open-loop fashion. That is, the patient implanted with the device has little or no control over the implant. The patient also has no computer or other automated system that assists in monitoring and/or programming the implanted device. However, implanted systems of increased complexity typically require an increased amount of monitoring and programming by an external user and/or an automated system. Communication to support such increased amount of monitoring and programming must be done more frequently.
By way of example, an implant patient may need to adjust the programmed settings of an implantable stimulator several times throughout the day, or an automated system may adjust the implant every few minutes when it is within communication range.
Complex implantable devices also typically require the exchange of a larger amount of data with an external user and/or an automated system than has heretofore been achievable. For example, an external user may want to frequently sample the readings of a number of implanted sensors as well as the current programmed settings, or an automated system may upload a significant volume of data as a time series of sensor readings. Additionally, rapidly changing signals such as an ECG, EEG, EMG, or ENG require high communication data rates in order to be communicated to an external device in a reasonable period of time.
Representative communication and/or control links with implantable medical devices are as described in the following U.S. Pat. No. 5,800,473: Systems, methods, and apparatus for automatic updating of a programmer for an active implantable medical device; U.S. Pat. No. 4,586,508: Implant communication system with patient coil; U.S. Pat. No. 4,532,932: Implant communication system with frequency shift means; U.S. Pat. No. 6,135,949: Apparatus for monitoring and/or controlling a medical device; U.S. Pat. No. 6,115,636: Telemetry for implantable devices using the body as an antenna; U.S. Pat. No. 6,106,551: Communication method for implantable medical device; U.S. Pat. No. 6,053,887: Medical treatment apparatus and method; U.S. Pat. No. 6,045,513: Implantable medical device for tracking patient functional status; and U.S. Pat. No. 6,024,539: Systems and methods for communicating with ambulatory medical devices such as drug delivery devices. All of these prior art approaches suffer from one or more deficiencies.
It is thus evident that there is a need in the art for an improved communication and control link with an implantable device, particularly implantable medical devices that are more complex and sophisticated than prior art implantable devices.